Method for manufacturing an inductive write element employing bi-layer photoresist to define a thin high moment pole pedestal

ABSTRACT

An inductive write element for use with a magnetic data recording and retrieval system is provided. The write element includes a magnetic yoke having an electrically conductive coil passing there through. The yoke is constructed of first and second magnetic poles, and performance of the write element is improved by the inclusion of a very thin pedestal of a high magnetic moment material on the first pole in the pole tip region. Further performance gains are realized by providing a tapered edge on the pedestal to facilitate magnetic flux flow through the pedestal.

FIELD OF THE INVENTION

This invention relates generally to magnetic disk storage systems, andmore particularly to write heads having low height, high momentpedestals.

BACKGROUND OF THE INVENTION

Magnetic disk drives are used to store and retrieve data for digitalelectronic apparatus such as computers. In FIGS. 1A and 1B, a magneticdisk data storage system 10 of the prior art includes a sealed enclosure12, a disk drive motor 14, one or more magnetic disks 16, supported forrotation by a drive spindle 13 of motor 14, and an actuator 18 includingat least one arm 20, the actuator being attached to an actuator spindle21. Suspensions 22 are coupled to the ends of the arms 20, and eachsuspension supports at its distal end a read/write head or transducer24. The head 24 (which will be described in greater detail wit referenceto FIGS. 2A and 2B) typically includes an inductive write element with asensor read element As the motor 14 rotates the magnetic disk 16, asindicated by the arrow R, an air bearing is formed under the transducer24 causing it to lift slightly off the surface of the magnetic disk 16,or, as is termed in the art, to “fly” above the magnet disk 16.Alternatively, some transducers, known as contact heads, ride on thedisk surface. Various magnetic “tracks” of information can be written toand/or read from the magnetic disk 16 as the actuator 18 causes thetransducer 24 to pivot in a short arc. The design and manufacture ofmagnetic disk data storage systems is well known to those skilled in theart.

FIG. 2A shows the distal end of the head 24 having a write element 26.The write element 26 is shown enlarged and with portions exposed forclarity. The write element 26 includes a magnetic yoke 28 having anelectrically conductive coil 30 passing therethrough.

The write element 26 can be better understood with reference to FIG. 2B,which shows the write element 26 and an integral read element 32 incross section. The head 24 includes a substrate 34 above which the readelement 32 and the write element 26 are disposed. An edge of the readelement 32 and of the write element 26 also define an air bearingsurface ABS, in a plane 36, which can be aligned to face the surface ofthe magnetic disk 16 (see FIGS. 1A and 1B). The read element 32 includesa first shield 38, a second shield 40, and a read sensor 42 that islocated within a dielectric medium 44 between the first shield 38 andthe second shield 40. The most common type of read sensor 42 used in theread/write head 24 is the magnetoresistive (AMR or GMR) sensor, which isused to detect magnetic field signal changes in a magnetic medium bymeans of changes in the resistance of the read sensor imparted from thechanging magnitude and direction of the magnetic field being sensed.

The write element 26 is typically an inductive write element thatincludes the second shield 40 (which functions as a first pole for thewrite element) and a second pole 46 disposed above the first pole 40.Since the present invention focuses on the write element 26, the secondshield/first pole 40 will hereafter be referred to as the “first pole”.The first pole 40 and the second pole 46 contact one another at abackgap portion 48, with these three elements collectively forming theyoke 28. The combination of a first pole tip portion and a second poletip portion near the ABS are sometimes referred to as the yoke tipportion 50. A write gap 52 is formed between the first and second poles40 and 46 in the yoke tip portion 50. The write gap 52 is filled with anon-magnetic, electrically insulating material that forms a write gapmaterial layer 54. This non-magnetic material can be either integralwith (as is shown here) or separate from a first insulation layer 56that lies upon the first pole 40 and extends from the yoke tip portion46 to the backgap portion 40. The conductive coil 30, shown in crosssection, passes through the yoke 28, sitting upon the write gap material54. A second insulation layer 58 covers the coil and electricallyinsulates it from the second pole 46.

An inductive write head such as that shown in FIGS. 2A and 2B operatesby passing a writing current through the conductive coil 30. Because ofthe magnetic properties of the yoke 28, a magnetic flux is induced inthe first and second poles 40 and 46 by write currents passed throughthe coil 30. The write gap 52 allows the magnetic flux to fringe outfrom the yoke 28 (thus forming a fringing gap field) and to cross amagnetic recording medium that is placed near the ABS.

With reference to FIG. 2C, a critical parameter of a magnetic writeelement is the trackwidth of the write element, which defines trackdensity. For example, a narrower trackwidth can result in a highermagnetic recording density. The Width is defined by the geometries inthe yoke tip portion at the ABS. In some newer designs a pedestal 60 isconstrued of a high magnetic moment material (high B_(sat)), having awidth W3. The high B_(sat) pedestal promotes concentration of magneticflux in the yoke tip region 50 of the write element 26. As can be seenfrom this view, the first and second poles 40 and 46 can have differentwidths W2 and W1 respectively in the yoke tip portion 50. The pedestalhas a width W3, which in some implementations can have the same width asthat of the second pole W1, as when the pedestal is created by a selfaligning process.

With reference to FIG. 2B, the fringing gap field of the write elementcan be further affected by the positioning of the zero throat level ZT.ZT is defined as the distance from the ABS to the first divergencebetween the first and second pole, and it can be defined by either thefirst or second pole 40, 46 depending upon which has the shorter poletip portion. If the first pole 40 includes a pedestal 60, then ZT isusually defined by the pedestal depth. The pedestal provides a welldefined ZT. In order to prevent flux leakage from the second pole 46into the back portions of the first pole 40, it is desirable to providea zero throat level in a well defined plane which is parallel to theplane of the ABS. Thus, accurate definition of the trackwidth, and zerothroat is critical during the fabrication of the write element.

The performance of the write element is further dependent upon theproperties of the magnetic materials used in fabricating the poles ofthe write element. In order to achieve greater overwrite performance,magnetic materials having a high saturation magnetic flux densityB_(sat) are preferred. A common material employed in forming the polesis high Fe content (55 at % Fe) NiFe alloy having a B_(sat) of about 16kG. However, high Fe content NiFe alloy has a high magnetostrictionconstant λs (on the order of 10⁻⁵) which causes undesirable domainformation in the poles. It is known that the domain wall motion in thewriter is directly related to the increase in popcorn noise in the readelement, especially when the motion occurs in the first pole, which alsoserves as a shield for the read element.

A reduction in popcorn noise in the read element can be achieved throughthe use of soft magnetic materials, (i.e. materials having a lowmagnetostriction constant) in the fabrication of the first pole 40.However, such materials generally have limited B_(sat). In order topromote concentration of magnetic flux density in the yoke tip region, ahigh B_(sat) material is used to form the pedestal 60.

The size and shape of the pedestal has dramatic affect on the flow ofmagnetic flux in the yoke tip region 50. For example, the abrupt anglebetween the pedestal 60 and the rest of the first pole 40 inhibits fluxflow and can lead to choking or saturation of flux. In addition, a thickpedestal (i.e. in the direction from the first pole 40 to the write gap52) causes further choking of the flux and also leads to poorly definedsignal pulses. Therefore, accurate control of pedestal size and shape iscritical. Creating a pedestal which is sufficiently thin and also has adesirable shape has been limited by available manufacturing techniques.For example, existing manufacturing techniques which employ CMP can notbe used to construct a pedestal with a tightly controlled thickness,thus limiting the pedestal to an overall minimum size.

Therefore, there remains a need for a process for manufacturing adesired thin pedestal. The process would necessarily allow tightercontrol of thickness than is possible with previous processes and wouldalso allow the shape of the pedestal to be controlled to soften theangle of the transition between the pedestal and the rest of the firstpole 40. In addition, the process would allow the pedestal to beconstructed of a high B_(sat) material, many of which materials must besputter deposited.

SUMMARY OF THE INVENTION

The present invention provides a method for manufacturing a writeelement for use in a magnetic data recording system, the write elementhaving a thin pedestal having a well controlled shape and size. A firstpole is constructed of a soft magnetic material. A layer of high B_(sat)material is then deposited onto the magnetic material of the first pole.A bi-layer photoresist is patterned onto the layer of high B_(sat)material in a pattern corresponding to the desired pedestal shape. Thehigh B_(sat) material layer is then etched, forming a pedestal with atapered edge, by removing material from the region not covered by thebi-layer photoresist A first insulation layer is then deposited, and thebi-layer photoresist is subsequently lifted off. Thereafter, a layer ofwrite gap material is deposited and an electrically conductive coil isformed on the write gap material. A second insulation layer is applied,and a second pole is formed so as to be electrically connected with thefirst pole.

The etching can be performed in such a manner that the edge of thepedestal can be a smoothly tapered. This advantageously promotes smoothflux flow through the pole tip region of the first pole. In addition,the process allows the high B_(sat) material to be sputter deposited.This is advantageous in that currently available high B_(sat) materialscannot be plated and must, therefore, be sputter deposited.

Another aspect of the invention is that it allows excellent control ofpedestal thickness. One reason that the thickness of the pedestal can betightly controlled is that chemical mechanical polishing is notrequired. CMP processes remove material in a manner which is difficultto accurately control, and therefore a relatively large tolerance inpedestal thickness would be required if such a process were used.

The bi-layer photoresist includes a first layer and a second layer thatcovers and extends beyond the edge of the first layer. The portion ofthe second layer extending beyond the first layer creates an overhang.When the first insulation layer is subsequently applied, the firstinsulation layer will form a smooth tapered edge terminating beneath theoverhang. The termination point of the insulation layer can becontrolled by the amount of overhang on the bi-layer photoresist or canalso be controlled by the manner in which the first insulation layer isdeposited. Although the deposited first insulation layer will cover thephotoresist, the portion under the overhang will be accessible tochemicals for lifting off the photoresist.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the following detaileddescription taken together with the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, withlike reference numerals designating like elements.

FIG. 1A is a partial cross-sectional front elevation view of a magneticdata storage system of the background art;

FIG. 1B is a top plan view taken along line 1B—1B of FIG. 1A;

FIG. 2A is a plan view of a read/write head of the background art, takenfrom 2A—2A of FIG. 1B, shown enlarged;

FIG. 2B is a view taken from line 2B—2B of FIG. 2A, shown enlarged;

FIG. 2C is a view taken from line 2C—2C of FIG. 2B;

FIG. 3 is a cross sectional view similar to FIG. 2B showing a read/writehead of the present invention;

FIG. 4 is a flow diagram of a process for producing a read/write head ofthe present invention; and

FIGS. 5-9 show the read write head of the present invention in various,intermediate stages of manufacture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 3, the present invention is embodied in acombination read/write head, generally designated 61, having merged readand write elements 62, 64, construction of the read element having beenpreviously discussed in the background of the invention with referenceto FIGS. 1A through 2C. The write element 64 includes first and secondmagnetic poles 66, 68, which join to form a magnetic yoke 70. Anelectrically conductive coil 72 passes through the interior of the yoke70, and is electrically isolated therefrom. The first magnetic poleincludes at its pole tip portion a pedestal 74 which will be describedin greater detail below.

With continued reference to FIG. 3, the first pole 66 is primarilyconstructed of a soft magnetic material (i.e. low magnetorestriction). Apedestal 74 is formed on the first pole 66 at the pole tip region,constructed of a high B_(sat) material. The pedestal is very thin,preferably between 0.1 and 1.0 μm, and more preferably less than 0.5 μm.The pedestal has a smoothly tapered edge 76. The smoothly tapered edge76 facilitates the smooth flow of magnetic flux through the pole tipregion of the first pole 66.

A first insulation layer 78 covers the first pole 66, and terminates atthe pedestal 74. The first insulation layer 78 preferably terminates ina smoothly tapered edge which ends near the apex of the tapered edge asshown in FIG. 3. Depending upon design requirements, the tapered edge ofthe first insulation layer can be located at various locations relativeto the pedestal 74. For example, if desired, the first insulation layer78 can be formed to terminate at the upper surface of the pedestalbeyond the tapered edge 76. Alternatively, if desired, the edge of thefirst insulation layer can be formed to end along the tapered edge 76 ata lower point away from the apex and toward the termination of thetapered edge 76. The first insulation layer 78 is preferably formed ofAl₂O₃ which is sputter deposited. However, as will be appreciated bythose skilled in the art, other dielectric materials can be used aswell.

With continued reference to FIG. 3, a layer of write gap material 80sits atop the first insulation layer 78 and the pedestal 74. The writegap material is preferably constructed of silicon, but can also beconstructed of other dielectric materials such as Al₂O₃. Theelectrically conductive coil 72 includes a plurality of winds, with aportion of each wind passing through the yoke 70. The coil sits atop thewrite gap material layer 80. The coil is preferably constructed ofcopper (Cu) and is manufactured according to a photolithographicprocess, which will be familiar to those skilled in the art.

With further reference to FIG. 3, a second insulation layer 81 coversthe coil 72 and electrically insulates it from the yoke 70. The secondinsulation layer 81 is preferably constructed of cured photoresist whichis deposited by a pbotolithographic process and cured at a hightemperature. the second pole 68 covers the second insulation layer 81and electrically couples with the first pole 66 at a backgap region 82to form the yoke 70.

With reference to FIG. 4, a process 84 for constructing the writeelement 64 of the present invention will be described. The read element62 having been partially constructed according to methods familiar tothose skilled in the art, the process 84 begins with a step 86 ofproviding the first pole 66. The first pole 66 is preferably formed of anickel iron alloy NiFe by a plating process which will be familiar tothose skilled in the art, but can also be deposited by sputtering andcan be formed of another soft magnetic material. Then, in a step 88 aprotective layer of alumina (Al₂O₃) is sputter deposited to provideelectrical insulation between S1 and a read element interconnect (notshown). Then, in a step 90 vias (not shown) are provided for a set ofread sensor leads (also not shown). The leads vias are formed by a wetetch process which will be familiar to those skilled in the art.Thereafter, in a step 92 a read element interconnect is formed (notshown). The interconnect is electroplated copper formed to about 1.0 to1.5 μm, which is thinner than the final target thickness of the firstpole 66 (FIG. 3). Thereafter, in a step 94 another layer of Al₂O₃ isdeposited and planarized using a chemical mechanical polishing process.This results in a layer of insulation 95 having a smooth upper surface(FIG. 3), which is flush with a smooth upper surface of the first pole66. The chemical mechanical polishing process preferably results in afirst pole 66 that is 1.5-3 μm thick.

With continued reference to FIG. 4, in a step 96 a layer 120 of highB_(sat) material is deposited This layer is deposited as a thin film,which is preferably deposited onto the first pole 66 and insulation 95either by sputtering or electroplating, as can be seen in FIG. 5. In oneembodiment of the invention, the high B_(sat) material is FeXN, whereinX is one or more of Rh, Ta or Al. This material can be either sputterdeposited in a single layer or applied as a plurality of laminatedfilms, and is preferably deposited to a thickness of 0.1-1.0 μm, or morepreferably less than 0.5 μm. Thereafter, in a step 98, aphotolithography process is used to form a bi-layer photoresist 100which can be more clearly understood with reference to FIG. 6. Thebi-layer photoresist is formed to pattern the pedestal 74, and includesa bottom layer 112, and an upper layer 114 which extends beyond thefirst layer forming an overhang 116. Thereafter, in a step 118, an ionmilling process is performed to selectively remove unwanted high B_(sat)material, forming the pedestal 74 as can be seen with reference to FIG.7. The ion milling process is preferably performed so as to form adesirable sloped or tapered edge 76 on the pedestal 74.

With continued reference to FIG. 4, in a step 122 a layer of Al₂O₃ 124is deposited. With reference to FIG. 8 it will be appreciated that theAl₂O₃ insulation layer 124 as deposited covers the first pole 66 and thebi-layer photoresist 100. In addition, the insulation layer 124partially covers the portion of the pedestal covered by the overhang 116of the bi layer photoresist 100. The insulation layer terminates in asmoothly tapered edge, and the location at which the insulationterminates can be controlled by controlling the amount of overhang ofthe bi-layer photoresist 100 and can also be controlled by thedeposition process used to deposit the insulation layer. The location ofthe termination of the insulation layer can be controlled to within+/−0.25 μm of a predetermined target location relative to the taperededge of the pedestal. The insulation layer preferably has an edge whichterminates near the apex of the tapered edge of the pedestal, that is,at the point where the tapered edge meets the flat top of the pedestal.In addition, the insulation layer 124 preferably is formed to a heightthat is roughly the same as the height of the pedestal.

With reference still to FIG. 4, in a step 126 the bi-layer photoresist100 is lifted off. This is accomplished by applying a solvent. However,as will be appreciated by those skilled in the art, solvents used toremove such a photoresist will not dissolve the AL₂O₃. The overhang 116provided by the bi-layer photoresist 100 facilitates lifting off thephotoresist 100, by leaving a portion of the photoresist 100 uncoveredby Al₂O₃. Thus, the overhang 116 allows solvent to enter and contact thephotoresist in order to lift it off.

Thereafter, in a step 128, a layer of write gap material 80 isdeposited. Then, in a step 130, a coil 72 is formed. The coil ispreferably constructed of copper formed by a plating process which willbe familiar to those skilled in the art. Subsequently, in a step 132another insulation layer is deposited, thus forming the secondinsulation layer 81 discussed with reference to FIG. 3. Then, in a step134 the second pole 68 is formed. The second pole is constructed ofmagnetic material, such as for instance FeXN and can be formed bysputtering or plating as necessitated by the choice of material.

While the present invention has been particularly shown and describedwith reference to the preferred embodiments, it will be understood bythose skilled in the art that various changes in form and detail may bemade without departing from the spirit, scope, and teaching of theinvention. Accordingly, the disclosed invention is to be consideredmerely as illustrative and limited in scope only as specified in theappended claims.

What is claimed is:
 1. A method for forming an inductive write element,comprising the steps of: a. providing a first pole constructed of a softmagnetic material; b. depositing a high magnetic moment material uponsaid pole; c. depositing a bi-layer photoresist onto a portion of saidhigh magnetic moment material; d. etching said high moment material toremove a portion of the high moment material not covered by saidbi-layer photoresist; e. depositing a first insulation layer; f.removing said bi-layer photoresist; g. depositing a write gap materialonto said first insulation layer and at least a pedestal portion of saidhigh moment material; h. forming an electrical coil upon said write gapmaterial; i. depositing a second insulation layer upon said write gapmaterial and said electrically conductive coil; and j. forming a secondpole over said second insulation layer and a portion of said write gapmaterial, said second pole being electrically connected with said firstpole at a location distal from said pedestal portion.
 2. The method ofclaim 1, wherein said bi-layer photoresist is formed in a two stepprocess resulting in a first photoresist layer and a second photoresistlayer formed upon and extending beyond an edge of said first photoresistlayer.
 3. The method of claim 1 wherein said etching step is performedby ion milling.
 4. The method of claim 1 wherein said etching step formsa tapered edge on said high magnetic moment material.
 5. The method ofclaim 1 wherein said etching step forms a thin, high magnetic momentpedestal.
 6. The method of claim 1 wherein said high magnetic momentmaterial is a material including Fe and N.
 7. The method of claim 1wherein said high magnetic moment material is deposited by sputtering.8. The method of claim 1 wherein said first and second insulating layersare Al₂O₃.
 9. The method of claim 1 further comprising the step ofplanarizing said first pole using a chemical mechanical polishingprocess prior to deposit said high magnetic moment material.